Cholinergic synapses have adrenergic receptors and are modified by adrenergic drugs. The purpose of this project is to explore the mechanisms by which adrenergic drugs can modify cholinergic transmission in autonomic ganglia. Electrophysiological methods will be used to study the effects of d-amphetamine and tyramine on the isolated stellate ganglion of the hamster. d-Amphetamine produces both ganglionic blockade and ganglionic stimulation. These effects may be due to direct actions on adrenergic receptors, or to other direct or indirect actions of d-amphetamine. Adrenergic agonists and antagonists will be used to elucidate the mechanism for each of the ganglionic effects of d-amphetamine. Cocaine and desipramine potentiate the blocking action of norepinephrine, but neither of these drugs alters the blocking action of d-amphetamine. This effect of cocaine will be studied to determine the mechanism for the selective potentiation of norepinephrine. The interactions of norepinephrine with d-amphetamine, tyramine, and pargyline will be explored to determine whether these drugs also potentiate the actions of norepinephrine. This project should increase our understanding of the pharmacological role of adrenergic mechanisms in autonomic ganglia. Furthermore, it should expand our knowledge of the physiologial role of catecholamines in ganglionic transmission.